The classic diesel is founded on heavy, fine-grained iron castings, liberally
reinforced with webbing and aged prior to machining. Buttressed main-bearing caps, pressed into the block and
often cross-drilled, support the crankshaft. Pistons run against replaceable liners, whose metallurgy can be
precisely controlled. Some of the better engines, such as the Cummins shown above, feature straight-cut
timing gears, which are virtually indestructible.